An axially phased implosion of a cylindrical tube with a phase velocity exceeding the sound speed of the fill material acts as a peristaltic pump which drives a shock wave along the axis. The region behind the onset of the phased implosion forms a converging-diverging nozzle. When appropriately designed the flow approaches a steady state in which the shock is planar and propagates near the nozzle entrance. The steady-state flow and the approach toward it have been derived in a one-dimensional model. The steady-state nozzle flow is well characterized: uniform across the channel, simple and predictable in the axial direction. The flow in the converging section is very stable and not affected by the flow in the diverging section. These properties form the basis of an alternative shock tube design which is not limited in pressure by material strength of the tube wall. Experiments with a simple design have corroborated the theoretical predictions. A super-shock tube, in which the phased implosion is driven by high explosives, can reach extremely high pressures and energy densities. With a well characterized drive system, measurements of the steady-state shape of the nozzle can be used to determine the equation of state along an isentrope behind the axial shock. 5 refs., 4 figs
